금(I)촉매를 이용한 다양한 4-phenyl-2-cyclopentenones의 합성 연구
- 금(I)촉매를 이용한 다양한 4-phenyl-2-cyclopentenones의 합성 연구
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- The catalysis of organic reactions mediated by transition metals has become an essential tool for chemical synthesis. But gold complexes have only recently been investigated as a catalyst. In the past 10 years, a number of gold catalysis have been published. Gold-catalyzed reactions have a unique feature. Unlike many Lewis acids, gold catalysts are exceptionally alkynophilic. The most fundamental reactivity pattern in gold-catalysed reactions is the activation of a C-C multiple bond, in most cases an alkyne, for the attack of a nucleophile. This special feature has occupied the attention of synthetic chemist.
Of particular interest to organic chemists is methodology development towards the syntheses of carbocycles and heterocycles. Various synthetic methods to construct a wide range of carbocycles and hetereocycles using gold catalyst were reported in recent years. In these reports, cycles were made by intramoleculr addition of various carbon and heteroatom nucleophiles with activated alkyne by gold catalyst.
A highly efficient gold(I)-catalyzed reaction initiated by the addition of silyl ethers to alkynes has been developed. This gold(I)-catalyzed transformations are accomplished under mild conditions and they showed substituent tolerance. This catalytic reaction has synthetic advantage in that it provides highly functionalized 2-cyclopentenones possesing a quarternary carbon center.
The 'herbertanes", a small group of sesquiterpenes was synthesized using gold(I)-catalyzed reaction. Herbetanes group is containing sterically crowded 1-aryl-1,2,2-trimethyl-cyclopentane carbon framework with two vicinal quaternary carbon atoms on a cyclopentane ring. The herbertanes are interesting synthetic targets owing to the difficulty associated with the construction of vicinal quaternary carbon atoms on a framework. The interesting biological properties of the phenolic herbertanes make them important synthetic targets of current interest. The formal synthesis of (α)-herbertene, (α)-herbertenol, (β)-herbertenol and herbertenone A and B have been achieved. 5-Siloxypent-3-en-1-ynes were synthesized from ace-tophenones possessing various substituent on phenyl ring. And then gold(I)-catalyzed reactions as key-step were operated under mild conditions to give cyclopentenones in moderate yield and tolerate all cases. So this result demonstretes that gold(I)-catalyzed synthesis of 2-cyclopentenone can be applied to the synthesis of structural diverse and complex compound.
To achieve an enantioselective synthesis of cuparene, isomer of herbertene, a gold(I)-catalyzed reaction was pursed. If the chirality is transferred to the product in gold(I)-catalyzed reaction, this catalyzed reaction can be applied to enantioselective synthesis. To examine the possibility of chirality transfer, 5-siloxypent-3-en-1-yne having chirality was made by asymmetric dihydroxylation using AD-mix-α. And then this substrate was subjected to gold(I)-catalyzed synthesis of 2-cyclopentenone. The enantiomeric exess of substrate was almost transfered to the product. The synthesis of chiral substrate with high eneantiomeric exess is need to see the degree of chirality transfer.
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